Both evidence and motivation can be interpreted as internal versions of cause –

evidence: ‘I claim/you should believe that ... because ... ’;

motivation: ‘I want you/you are obliged to ... because ...’.

In general, orientation towards tenor is characteristic of ‘sharing’, ‘recommending’ and ‘exploring’ contexts, and also in principle of ‘enabling’ contexts of the ‘regulatory’ subtype (but see immediately below). In contrast, texts operating in contexts with an orientation towards field are much less likely to involve internal relations; instead, they are organised both globally and locally in terms of external relations.

Blogger Comment:

Note that this new addition to IFG by Halliday's reviser, Matthiessen, fails to alert the reader to the fact that Martin (1992) misunderstands the distinction between internal and external conjunctive relations. See, for example: